Saturn's Dazzling Rings Make It 'Rain'

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It's raining on Saturn, and the giant planet's amazing rings are
apparently the cause, scientists say.

A new study unveiled today has found that erosion from particles
making up the icy rings of Saturn are
forming rain water that falls on certain parts of the planet.

Scientists using the Keck Observatory in Hawaii have found that
tiny ice particles that compose the planet's distinctive rings
are sometimes eroded away and then deposited in the planet's
upper atmosphere. The droplets then create a kind of rain on the
planet. [ Amazing
photos of Saturn's rings ]

"We estimate that one Olympic-sized swimming pool of water is
falling on Saturn per day," James O'Donoghue, an astronomer at
the University of Leicester in the United Kingdom and an author
of the study, told SPACE.com in an email.

It's raining on Saturn

By using data from the
Keck Observatory collected over the course of two hours in
2011, O'Donoghue and his team were able to observe pieces of the
ringed planet that have never been mapped in such exquisite
detail.

The team found that charged water molecules rain down only on
certain parts of the planet, which show up darker in infrared
images. O'Donoghue found a connection between those parts of
Saturn and the parts of the rings heavy in ice.

"The most surprising element to us was that these dark regions on
the planet are found to be linked — via magnetic field lines — to
the solid portions of water-ice within Saturn's ring-plane,"
O'Donoghue said.

The magnetic connection creates a pathway for small ice particles
in the rings to slough off into the planet's atmosphere, causing
the "ring rain."

Because O’Donoghue and his group located the source of the ring
rain, it might now be possible to work backwards to see how those
charged water particles became vulnerable to erosion in the first
place.

The research is detailed online in the April 10 edition of the
journal Nature.

Saturn's ringed past

Most of the mass in Saturn's
rings today is separated into "boulders" that are a few
centimeters in diameter, but scientists have never pinned down
the evolutionary past of the rings. Planetary scientists do know
that the rings have not always been so clumped, Jack Connerney,
an astrophysicist working with NASA who wasn't involved with the
study, told SPACE.com.

"So what you have to do is get your mind around the idea that
over millions of years, that boulder has not been a boulder,"
Connerney, who wrote a commentary on O'Donoghue's study in
Nature, added. "Mass is transferred from one boulder to next, and
while it's transferred, [the particles are] vulnerable to erosion
mechanisms."

This could account for why O'Donoghue and his team saw rainfall
on the gas giant.

O’Donoghue's study also could help further explain why each of
Saturn's rings is a different density and size. The magnetic
field that makes it rain in certain areas of the planet also
could control the space and composition of the rings.

"It's quite possible that the rings we see today were shaped — or
sculpted — by this process," Connerney added. "So, yes, acting
over millions of years this process can remove mass from the ring
plane, and who knows — a few tens of millions of years from
now it can look quite different."